Peculiarities of Periodontal Pocket Microbiome in Patients with Generalized Periodontitis in the Post-COVID Period

Abstract

The oral cavity, like the lungs, is often referred to as the «ecological niche of commensal, symbiotic, and pathogenic organisms», and the emigration and elimination of microbes between them are constant, ensuring a healthy distribution of saprophytic microorganisms that maintains organ, tissue, and immune homeostasis. The prolonged hospital stays due to COVID-19 complications, cross-infection, oxygenation therapy through the mask or incubation, and long-term intravenous infusions limit the patient’s ability to care about the oral cavity, regularly clean teeth, floss interdental, etc., which creates extremely favorable conditions for colonization by aerobic and anaerobic pathogens of the oral cavity and periodontal pockets and leads to the rapid progression of chronic generalized periodontitis in this category of patients in the future. The goal of the study was to assess the state of the microbiome of the periodontal pockets of dental patients in the post-covid period. Methods. The object of the study was 140 patients with generalized periodontitis of the I and II stages of development in the chronic course (GP), among which 80 patients had coronavirus disease in the closest past. The patients were randomized by age, sex, and stage of GP development. The diagnosis of periodontal disease was established according to the classifi cation by Danilevskyi. The bacteriological material for aerobic and facultative anaerobic microflora and yeast-like fungi was collected from periodontal pockets with a calibrated bacteriological loop and immediately seeded on blood agar. Results. Significant qualitative and quantitative changes in the nature of the oral microbiocenosis were observed in patients with GP after the recent coronavirus disease, compared with similar patients who did not suffer from COVID-19. We have noticed almost complete disappearance of bacteria that belong to the transient representatives of the oral microflora such as Neisseria, corynebacteria (diphtheria), micrococci, and lactobacilli. The main resident representatives of the oral microflora, i.e., α-hemolytic Streptococci of the mitis group, were found in all healthy individuals and patients of groups A and C, but in 30.0±4.58% of patients in group B, α-hemolytic streptococci in the contents of periodontal pockets are present in quantities not available for detection by the applied method (<2.7 lg CCU/mL). In terms of species, Streptococcus oralis and Streptococcus salivarius are more characteristic in gingival crevicular fluid in healthy individuals (93.8% of selected strains). In 68.4±3.32% of patients in group A, 64.0±3.43% of patients in group B, and 67.5±3.76% of patients in group C, the dominant species were Streptococcus gordonii and Streptococcus sanguinis (p<0.01), which increased pathogenic potential as they produce streptolysin-O, inhibit complement activation, bind to fibronectine, actively form biofilms on the surface of tooth enamel and gum epithelial surface, and can act as an initiator of adhesion of periodontal pathogens. The other representatives of the resident microflora of the oral cavity — Stomatococcus mucilaginosus and Veillonella parvula for the patients of group C are also found in periodontal pockets with a signifi cantly lower index of persistence and minimal population level. In the post-covid period, both the population level and the frequency of colonization of periodontal pockets by Staphylococci and β-hemolytic Streptococci decreases rapidly. For these patient groups, unlike for those that did not suff er from COVID-19, we did not find any case of colonization with Staphylococcus aureus, as well as β-hemolytic Streptococci and epidermal Staphylococcus were also absent. The most characteristic in the post-covid period is a decrease in the proportion of α-hemolytic Streptococci, an increase in the proportion of yeast-like fungi of Candida species, as well as the appearance of a significant number of gram-negative rod-shaped bacteria (Enterobacteria and Pseudomonads). In periodontal patients, the microbial count is approximately 2 orders of magnitude lower than in those with GP who did not suffer from COVID-19 (p<0.05). Conclusions. The overpassed coronavirus disease due to intensive antibiotic therapy leads to a marked decrease in the number of viable saprophytic microorganisms in the periodontal pockets of patients with GP. In the post-covid period for the patients with GP, there is a decrease in the level of colonization of periodontal pockets by species of resident oral microflora — α-hemolytic Streptococci, reduction of resident microorganism’s species, and almost complete disappearance of transient microfl ora. On the other hand, the frequency of colonization of periodontal pockets by fungi species, enterobacteria, and pseudomonads significantly increases. There are more expressed disorders in the periodontal pocket’s microbiome for the patients with a severe and complicated course of coronavirus disease, such as post-covid pulmonary fibrosis, which requires reconsideration of approaches to therapeutic and pharmacological treatment in this category of patients.